The role of esophageal longitudinal muscle in motility disorders of the esophagus is unclear. Traditional manometric techniques do not assess contraction of this muscle. The advent of a new catheter-based ultrasound probe has produced high-quality intraluminal images of the esophagus which allows for in vivo study of the esophageal longitudinal muscle. We aim to use this ultrasound probe to study patients with chest pain of noncardiac origin in an effort to further define the pathophysiologic mechanisms responsible for symptoms in these patients. Ten patients with noncardiac chest pain and 14 patients with heartburn have been studied using simultaneous intraluminal pressure, pH and ultrasound probe. Approximately 100 of chest pain events were recorded and 96% of those we have analyzed showed sustained esophageal contraction lasting a mean of 72.5 seconds. This motor pattern was not accompanied by changes in intraluminal pressure. There is a strong temporal correlation between a previously unrecognized esophageal motor event, sustained esophageal contraction and spontaneous esophageal chest pain. We also found that at the time when patients experienced chest pain, 9 out of 24 events were accompanied with acid reflux and all of them were related with sustained contraction. During asymptomatic control period, those events with acid reflux were also accompanied with sustained contraction. Our future plans are to analyze the role of acid reflux and the role of transient lower esophageal sphincter relaxation in relation with symptoms such as chest pain and heartburn.